Radio frequency spectrum is a scarce and critical natural resource that is utilized for many services including surveillance, navigation, communication, and broadcast- ing. Recent years have seen tremendous growth in the use of spectrum especially by commercial cellular operators. Ubiquitous use of smartphones and tablets is one of the reasons behind an all-time high utilization of spectrum. As a result, cellular operators are experiencing a shortage of radio spectrum to meet bandwidth demands of users. On the other hand, spectrum measurements have shown that much spectrum not held by cellular operators is underutilized even in dense urban areas. This has motivated shared access to spectrum by secondary systems with no or minimal impact on incumbent systems. Spectrum sharing is a promising approach to solve the problem of spectrum congestion as it allows cellular operators access to more spectrum in order to satisfy the ever-growing bandwidth demands of commercial users.
標簽： Spectrum Sharing Between Radars
上傳時間： 2020-06-01
上傳用戶：shancjb
Switched systems are embedded devices widespread in industrial applications such as power electronics and automotive control. They consist of continuous-time dynamical subsystems and a rule that controls the switching between them. Under a suitable control rule, the system can improve its steady-state performance and meet essential properties, such as safety and stability, in desirable operating zones.
標簽： Invariance Switching Analysis1 Systems by
上傳時間： 2020-06-07
上傳用戶：shancjb
This manuscript is a partial draft of a book to be published in early 1994 by AddisonWesley (ISBN 0-201-63337-X). Addison-Wesley has given me permission to make drafts of the book available to the Tcl community to help meet the need for introductory documentation on Tcl and Tk until the book becomes available. Please observe the restrictions set forth in the copyright notice above: you’re welcome to make a copy for yourself or a friend but any sort of large-scale reproduction or reproduction for profit requires advance permission from Addison-Wesley
標簽： Toolkit
上傳時間： 2020-07-05
上傳用戶：
The PW8205A8TS is the highest performance trench N-ch MOSFETs with extreme high cell density,which provide excellent RDSON and gate charge for most of the small power switching and loadswitch applications. The meet the RoHS and Product requirement with full function reliabilityapproved .
標簽： 8205a8
上傳時間： 2022-02-14
上傳用戶：wangshoupeng199
本系統采用電動機電樞供電回路串接采樣電阻的方式來實現對小型直流有刷電動機的轉速測量。該系統主要由二階低通濾波電路,小信號放大電路、單片機測量顯示電路、開關穩壓電源電路等組成。同時自制電機測速裝置,用高頻磁環作為載體,用線圈繞制磁環,利用電磁感應原理檢測電機運行時的漏磁,將變化的磁場信號轉化為磁環上的感應電流。用信號處理單元電路將微弱電信號轉化為脈沖信號,送由單片機檢測,從而達到準確測量電機的速度的要求。In this system, the sampling resistance of armature power supply circuit is connected in series to measure the speed of small DC brush motor. The system is mainly composed of second-order low-pass filter circuit, small signal amplifier circuit, single-chip measurement and display circuit, switching regulated power supply circuit and so on. At the same time, the self-made motor speed measuring device uses high frequency magnetic ring as the carrier, coil winding magnetic ring, and electromagnetic induction principle to detect the leakage of magnetic field during the operation of the motor, which converts the changed magnetic field signal into the induced current on the magnetic ring. The weak electric signal is transformed into pulse signal by signal processing unit circuit, which is sent to single chip computer for detection, so as to meet the requirement of accurate measurement of motor speed.
標簽： 直流電動機
上傳時間： 2022-03-26
上傳用戶：
隨著光伏發電系統快速發展,以及電動汽車充電樁的普及,傳統的剩余電流保護器無法滿足實際需求。介紹了一款B型剩余電流保護器,采用磁調制剩余電流互感器和零序電流互感器采集剩余電流。根據GB/T 22794—2017標準要求,可識別1 kHz及以下的正弦交流、帶和不帶直流分量的脈動直流、平滑直流等剩余電流信號。經信號調理電路將電壓信號送到單片機進行采集和判斷。通過試驗測試,該樣機在測試精度和速度上均符合國家標準的相關要求。The rapid development of photovoltaic power generation systems and the popularity of electric vehicle charging piles make the traditional residual current protective devices unable to meet the actual demand.This paper proposed a type B residual current protective device,which uses the magnetically modulated residual current transformer and the zero sequence current transformer to acquire the residual current.According to the requirements of GB/T 22794—2017,the type B residual current protective device can detect sinusoidal AC residual current of 1kHz and below 1kHz,pulsating DC residual current with and without DC component,smooth DC residual current and so on.The signal processing circuit sends the voltage signal to the MCU for acquisition and judgment.Through experimental tests,the device meets the relevant requirements of national standards in terms of test accuracy and speed.
標簽： 電流保護器
上傳時間： 2022-03-27
上傳用戶：
為適應雙向DC/DC功率變換的電流采樣需求,一種高精度高邊電流采樣電路被提出。其基本思想是在功率電路的高邊串入采樣電阻,借助電流鏡原理并引入偏置電流電路,將雙向電流均轉換為正向電壓輸出。通過理論分析與仿真結合的方法對電流鏡采樣原理及4種不同的偏置電流電路方案進行對比,最后通過實驗數據驗證了高精度高邊電流采樣電路的有效性。實驗數據表明,該采樣電路可在-25~75℃的溫度工作范圍內,針對-10~＋10 A范圍內的電流采樣實現優于5%的采樣精度。Current sensing plays an important role in controlling,monitoring or protection functions of power systems.To meet the current sensing requirement of bidirectional DC/DC converters,a high-accuracy bidirectional current sensing circuit is proposed.The proposed current sensing circuit inserts a resistor in the path of the current to be sensed,while the current mirror and biased current circuit are introduced.Therefore,the bidirectional current can be expressed by positive voltage.By theoretical analysis and simulation,the sampling theory is analyzed and four biased current circuits are compared.At last,experimental results verified the proposed method.It is demonstrated that the proposed current sensing circuit can achi...
上傳時間： 2022-04-22
上傳用戶：
為解決移相全橋電路驅動及相角控制問題,設計了一種數字控制的移相全橋驅動電路.以TPL521為光耦隔離、IR2110為柵極驅動芯片.由DSP產生PWM信號,經過光耦隔離和邏輯電路后送至IR2110進行相角控制.文章對IR2110驅動電路原理進行分析及參數進行設計,對TMS320F28335進行設置并給出部分代碼.實驗結果表明：通過TMS320F28335可產生的不同相角的PWM波形,滿足了移相全橋對不同相角控制的要求.In order to solve the problem of phase-shifted full-bridge circuit driving and phase angle control,a digitally controlled phaseshifted full-bridge driving circuit was designed. TPL521 optocoupler isolation,IR2110 gate driver chip. PWM signals are generated by the DSP and sent to the IR2110 for phase angle control after optocoupler isolation and logic circuits. This text carries on the analysis to the principle of IR2110 drive circuit and parameter design,set up and give out some code to TMS320F28335. The experimental results show that the PWM waveforms with different phase angles generated by TMS320F28335 can meet the requirements of phase-shifted full-bridge control for different phase angles.
上傳時間： 2022-05-03
上傳用戶：zhanglei193
基于DSP28035的高速永磁無刷直流電機驅動系統，包括論文和軟硬設計資料。摘要參賽作品為基于DSP28035的高速永磁無刷直流電機驅動系統。該系統以一臺額定轉速60 krpm的高速永磁無刷直流電機、交錯并聯的Buck電路以及全橋電路為硬件平臺，以DSP28035為控制核心，實現了調壓調速功能和基于坐標變換的無位置傳感器新技術。為實現該系統要求，本作品充分利用了DSP28035的資源例如：CLA模塊，模擬比較器、HPWM模塊以及AD轉換模塊等。AbstractThis work is the drive system for a high speed permanent magnet burshless dc motor based on DSP28035. The hardware platform consists of a BLDC motor(rated speed is 60000rpm), a Buck circuit and an inverter. Under the control of DSP28035, this system can achieve the goal of adjusting the motor’s speed with voltage and the function of sensorless control based on the coordinate transformation. By making full use of resources of the core, such as CLA, analog comparator, HPWM and AD converters, the whole system can meet the requirements.1 引言高速永磁無刷直流電機驅動系統由于基波頻率較高（一般在1kHZ以上），利用逆變橋斬波進行調速的控制方式通常會受到開關管開關頻率的限制，因此該系統多采用三相全橋前級加Buck電路進承擔調壓調速的功能，而三相全橋主要承擔邏輯換相的功能。然而，傳統Buck電路所需電感的體積較大，增加了系統的體積，降低了系統的功率密度。
上傳時間： 2022-05-08
上傳用戶：bluedrops
<li id="kwa24"></li>